1. Field of the Invention
The present invention relates to a processed object processing apparatus that processes objects to be processed, a processed object processing method, a pressure control method, a processed object transfer method, and a transfer apparatus, and in particular relates to a processed object processing apparatus that carries out CVD (chemical vapor deposition) or COR (chemical oxide removal) as an alternative to dry etching or wet etching, and more particularly, relates to a processed object processing apparatus comprising a plurality of treatment systems, a processed object transfer method for transferring the processed object therethrough, and a pressure control method for controlling a pressure therethrough.
2. Description of the Related Art
From hitherto, etching has been carried out to shape thin films using a chemical reaction. In general, the etching process forms a set with a lithography process; in the lithography process, a resist pattern is formed, and then in the etching process the thin film is shaped in accordance with the resist pattern that has been formed.
There are two types of etching, dry etching and wet etching. The most common type of dry etching is parallel plate reactive ion etching. With parallel plate reactive ion etching, a vacuum treatment chamber of a vacuum treatment apparatus (processed object processing apparatus) is put into a vacuum state, a wafer, which is an object to be processed, is put into the vacuum treatment chamber, and then an etching gas is introduced into the vacuum treatment chamber.
Inside the vacuum treatment chamber are provided a stage on which the wafer is placed, and an upper electrode which is parallel to and faces a wafer-placing surface of the stage. A high-frequency voltage is applied to the stage, whereupon the etching gas is made into a plasma. Charged particles such as positive and negative ions and electrons, neutral active species that act as etching species, and so on exist scattered around in the plasma. When an etching species is adsorbed onto a thin film on the wafer surface, a chemical reaction occurs at the wafer surface, and then products thus produced separate away from the wafer surface and are exhausted outside the vacuum treatment chamber, whereby etching proceeds. Moreover, depending on the conditions, the etching species may be sputtered onto the wafer surface, whereby etching proceeds through a physical reaction.
Here, the high-frequency electric field is applied to the wafer surface perpendicularly thereto, and hence the etching species (radicals) also move in a direction perpendicular to the wafer surface. The etching thus proceeds in the direction perpendicular to the wafer surface, rather than proceeding isotropically over the wafer surface. That is, the etching does not spread sideways across the wafer surface. Dry etching is thus suitable for microprocessing.
However, with dry etching, to carry out high-precision microprocessing conforming to a resist pattern, it is necessary to make the ratio between the etching rate for the material to be etched and the etching rate for the resist material high, and take care over etching damage caused by contamination with impurities, the occurrence of crystal defects and so on.
With wet etching, on the other hand, there is a dipping method in which the wafer is immersed in an etching bath containing a liquid chemical, and a spinning method in which a liquid chemical is sprayed onto the wafer while rotating the wafer. In either case, the etching proceeds isotropically, and hence sideways etching occurs. Consequently, wet etching cannot be used in microprocessing. Note, however, that wet etching is used even nowadays for processes such as completely removing a thin film.
Moreover, an example of a method of forming a thin film using a chemical reaction is CVD (chemical vapor deposition). With CVD, two or more reactant gases are reacted in the vapor phase or in the vicinity of the surface of a wafer or the like, and a product produced through the reaction is formed on the wafer surface as a thin film. At this time, the wafer is heated, and hence activation energy is supplied to the reactant gases by thermal radiation from the heated wafer, whereby the reaction of the reactant gases is excited.
Conventionally, in the manufacture of integrated circuits and other electronic devices for flat panel displays and so on, vacuum treatment apparatuses have been used to carry out various types of treatment such as film formation including CVD as described above, oxidation, diffusion, etching for shaping as described above, and annealing. Such a vacuum treatment apparatus is generally comprised of at least one load lock chamber, at least one transfer chamber, and at least one treatment chamber. At least two types of such vacuum treatment apparatus are known.
One type is a multi-chamber type vacuum treatment apparatus. Such a vacuum treatment apparatus is comprised of three to six process chambers as vacuum treatment chambers, a vacuum preparation chamber (load lock chamber) having a transfer mechanism for transferring semiconductor wafers, i.e. objects to be processed, into and out of each of the process chambers, a polygonal transfer chamber around which are disposed the process chambers and the load lock chamber and which has in peripheral walls thereof a plurality of connecting ports for communicating in gas-tight fashion with the process chambers and the load lock chamber via gate valves, and a transfer arm that is provided inside the transfer chamber and is able to turn, elongate and contract (see, for example, Japanese Laid-open Patent Publication (Kokai) No. H08-46013).
Moreover, the other type is a vacuum treatment apparatus having chambers in a straight line. Such a vacuum treatment apparatus has a vacuum treatment chamber in which etching is carried out on semiconductor wafers, and a load lock chamber having built therein a scalar type single pick type or scalar type twin pick type transfer arm as transfer means for carrying out handover of the wafers between the load lock chamber and the vacuum treatment chamber. That is, a vacuum treatment chamber and a load lock chamber having a transfer arm built therein are taken as one module (see, for example, Japanese Laid-open Patent Publication (Kokai) No. 2001-53131 and Japanese Laid-open Patent Publication (Kokai) No. 2000-150618).
In either of the types of vacuum treatment apparatus described above, switching between a vacuum state and an atmospheric pressure state is carried out in the load lock chamber, and smooth wafer transfer is realized between a loader that transfers the wafer set in a wafer carrier and a vacuum treatment chamber.
In the case of etching treatment, with either of the types of vacuum treatment apparatus, it has been that a high-frequency voltage is applied to an etching gas (reactive treatment gas) that has been introduced into a vacuum treatment chamber, thus making the reactive treatment gas into a plasma, whereby etching is carried out. With this dry etching, the etching treatment is carried out with excellent perpendicular anisotropy due to the etching species being controlled according to the applied voltage, and hence etching can be carried out in conformance with the required line width for lithography.
However, there have been advances in the development of microprocessing technology with regard to a photolithography process of burning circuit patterns onto wafer surfaces, and amid this a process in which exposure is carried out with ultraviolet radiation from a KrF excimer laser (wavelength 248 nm) as a photolithography light source has been put into practice, and moreover a process in which an ArF excimer laser having a yet shorter wavelength (193 nm) is used is in the process of being put into practice. Furthermore, photolithography using an F2 laser (wavelength 157 nm), which enables formation of a fine pattern of line width 70 nm or less, has become the top contender for the next-generation process of 2005. However, a resist material that enables 1:1 line-and-space fine patterning with a line width of 65 nm or less at a film thickness of 150 to 200 nm without loss of dry etching resistance has not yet been developed, and with conventional resist materials a practical problem of particle contamination due to outgassing arises, and hence fine patterning by anisotropic dry etching is approaching its limit.
There are thus hopes on COR (chemical oxide removal) as a fine etching treatment method as an alternative to dry etching or wet etching. With COR, gas molecules are subjected to chemical reaction and products produced are attached to an oxide film on an object to be processed (wafer), and then the wafer is heated to remove the product, whereby a line width finer than that of a lithography pattern can be obtained. Moreover, COR involves mild isotropic etching; the etching rate is controlled through parameters such as the pressure, the gas concentrations, the gas concentration ratio, the treatment temperature, the gas flow rates, and the gas flow rate ratio, and the etching stops through the treatment amount saturating beyond a certain treatment time period. The desired etching rate can thus be obtained by controlling the saturation point.
Such COR is suitable for the manufacture of a sub-0.1 μm metal oxide semiconductor field effect transistor device comprised of a minimum-thickness poly-depletion layer, source/drain junctions having a metal silicide layer formed thereon, and very low sheet resistance poly-gates, the manufacture using a damascene-gate process comprised of source/drain diffusion activation annealing, and metal silicidation which occurs immediately before a dummy gate region that is subsequently removed and replaced with a polysilicon gate region (see, for example, the specification of U.S. Pat. No. 6,440,808).
With vacuum treatment apparatuses that carry out conventional etching treatment, there are demands for it to be possible to carry out a plurality of processes more efficiently. Moreover, for vacuum treatment apparatuses that carry out COR treatment or CVD treatment, treatment to cool wafers that have been heated through the COR treatment or CVD treatment is required, and hence there are again demands for it to be possible to carry out a plurality of processes more efficiently. However, with conventional vacuum treatment apparatuses, as described above, switching between a vacuum state and an atmospheric pressure state is carried out in a load lock chamber, and yet the load lock chamber contains both a transfer arm and a cooling mechanism for cooling wafers, and hence the volume of the load lock chamber inevitably becomes large, and thus the switching between the vacuum state and the atmospheric pressure state requires much time. Moreover, a wafer that has been transferred into the load lock chamber is exposed to air convection due to the switching between the vacuum state and the atmospheric pressure state for a long time, and hence there is a risk of attachment of particles caused to fly up by the convection.